4. Hydrolysis stability

It expresses the behavior of an organic chemical derivative in the presence of water. The effect of water always shows up in the end, as it is virtually impossible to completely prevent contamination by water, which can also result from the degradation reaction of one or other of the fluid's constituents. While a base oil is, by its very nature, little affected by hydrolysis (as is the case, for example, with hydrocarbons), the additives it contains may, on the other hand, be sensitive to it.

Hydrolysis is a reaction between the molecule and water. It alters the molecule's structure. However, apart from any hydrolytic reaction, water retained in the oil can have a corrosive effect. Hydrolysis, combined with water contamination, manifests itself in several ways:

• changes in the physical properties of the fluid ;...